When you make an event with the event checklist, you get to design an event landing page. This landing page acts as an invitation to your event, and lets your guests see event details, add the event to their calendar, share it with their friends, or save it to their events. The Join Event button becomes active when your event starts, or at the time you choose if you add a buffer.  

When you add buffer time, up to 10 guests will be able to enter your Space when you specify (15, 30, or 60 minutes, 1 day, or 1 week before or after the event start/end time, or always open).

Why add buffer time? This is helpful to avoid bottlenecks at large events or when you want your guests to be able to test out Gather or explore your Space prior to the start of your event.